Improve Paged- and ScrollGui

- PagedGui pages and ScrollGui content is now saved as List<SlotElement> to improve performance
- Added PagedGui#bake and ScrollGui#bake to recreate those slot element lists if needed
- PagedInventoriesGuiImpl now lets oversized inventories overflow to the next page
- Added resize handler to VirtualInventory that is called whenever the inventory is resized
- PagedInventoriesGuiImpl and ScrollInventoriesGuiImpl automatically register a resize handler to virtual inventories that they display

invui-core/src/main/java/xyz/xenondevs/invui/gui/AbstractPagedGui.java

@@ -21,6 +21,8 @@ public abstract class AbstractPagedGui<C> extends AbstractGui implements PagedGu
     private int currentPage;
     
     private List<BiConsumer<Integer, Integer>> pageChangeHandlers;
+    protected List<C> content;
+    protected List<List<SlotElement>> pages;
     
     public AbstractPagedGui(int width, int height, boolean infinitePages, int... contentListSlots) {
         super(width, height);
@@ -93,7 +95,7 @@ public abstract class AbstractPagedGui<C> extends AbstractGui implements PagedGu
     }
     
     private void updatePageContent() {
-        List<SlotElement> slotElements = getPageElements(currentPage);
+        List<SlotElement> slotElements = (pages != null && !pages.isEmpty()) ? pages.get(currentPage) : List.of();
         
         for (int i = 0; i < contentListSlots.length; i++) {
             if (slotElements.size() > i) setSlotElement(contentListSlots[i], slotElements.get(i));
@@ -101,6 +103,23 @@ public abstract class AbstractPagedGui<C> extends AbstractGui implements PagedGu
         }
     }
     
+    @Override
+    public void setContent(@Nullable List<C> content) {
+        if (content == null || content.isEmpty()) {
+            this.content = List.of();
+            this.pages = List.of();
+            update();
+        } else {
+            this.content = content;
+            bake(); // calls update()
+        }
+    }
+    
+    @Override
+    public int getPageAmount() {
+        return pages != null ? pages.size() : 0;
+    }
+    
     @Override
     public int getCurrentPage() {
         return currentPage;
@@ -142,8 +161,6 @@ public abstract class AbstractPagedGui<C> extends AbstractGui implements PagedGu
         return pageChangeHandlers;
     }
     
-    protected abstract List<SlotElement> getPageElements(int page);
-    
     public static abstract class AbstractBuilder<C>
         extends AbstractGui.AbstractBuilder<PagedGui<C>, PagedGui.Builder<C>>
         implements PagedGui.Builder<C>

invui-core/src/main/java/xyz/xenondevs/invui/gui/AbstractScrollGui.java

@@ -1,6 +1,7 @@
 package xyz.xenondevs.invui.gui;
 
 import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
 import xyz.xenondevs.invui.gui.structure.Structure;
 import xyz.xenondevs.invui.util.SlotUtils;
 
@@ -24,6 +25,8 @@ public abstract class AbstractScrollGui<C> extends AbstractGui implements Scroll
     private int offset;
     
     private List<BiConsumer<Integer, Integer>> scrollHandlers;
+    protected List<C> content;
+    protected List<SlotElement> elements;
     
     public AbstractScrollGui(int width, int height, boolean infiniteLines, int... contentListSlots) {
         super(width, height);
@@ -109,6 +112,24 @@ public abstract class AbstractScrollGui<C> extends AbstractGui implements Scroll
         }
     }
     
+    @Override
+    public int getMaxLine() {
+        if (elements == null) return 0;
+        return (int) Math.ceil((double) elements.size() / (double) getLineLength()) - 1;
+    }
+    
+    @Override
+    public void setContent(@Nullable List<C> content) {
+        if (content == null || content.isEmpty()) {
+            this.content = List.of();
+            this.elements = List.of();
+            update();
+        } else {
+            this.content = content;
+            bake(); // calls update()
+        }
+    }
+    
     protected void update() {
         correctCurrentLine();
         updateControlItems();
@@ -116,7 +137,7 @@ public abstract class AbstractScrollGui<C> extends AbstractGui implements Scroll
     }
     
     private void updateContent() {
-        List<? extends SlotElement> slotElements = getElements(offset, contentListSlots.length + offset);
+        List<SlotElement> slotElements = getElements(offset, contentListSlots.length + offset);
         
         for (int i = 0; i < contentListSlots.length; i++) {
             if (slotElements.size() > i) setSlotElement(contentListSlots[i], slotElements.get(i));
@@ -124,6 +145,10 @@ public abstract class AbstractScrollGui<C> extends AbstractGui implements Scroll
         }
     }
     
+    protected List<SlotElement> getElements(int from, int to) {
+        return elements.subList(from, Math.min(elements.size(), to));
+    }
+    
     @Override
     public void setScrollHandlers(@NotNull List<@NotNull BiConsumer<Integer, Integer>> scrollHandlers) {
         this.scrollHandlers = scrollHandlers;
@@ -143,8 +168,6 @@ public abstract class AbstractScrollGui<C> extends AbstractGui implements Scroll
             scrollHandlers.remove(scrollHandler);
     }
     
-    protected abstract List<? extends SlotElement> getElements(int from, int to);
-    
     public abstract static class AbstractBuilder<C>
         extends AbstractGui.AbstractBuilder<ScrollGui<C>, ScrollGui.Builder<C>>
         implements ScrollGui.Builder<C>

invui-core/src/main/java/xyz/xenondevs/invui/gui/PagedGui.java

@@ -219,6 +219,14 @@ public interface PagedGui<C> extends Gui {
      */
     void setContent(@Nullable List<@NotNull C> content);
     
+    /**
+     * Bakes and updates the pages of this {@link PagedGui} based on the current content.
+     * <p>
+     * This method does not need to be called when using {@link #setContent(List)},
+     * but is required when the size of the content itself changes.
+     */
+    void bake();
+    
     /**
      * Gets the registered page change handlers.
      *

invui-core/src/main/java/xyz/xenondevs/invui/gui/PagedInventoriesGuiImpl.java

@@ -4,11 +4,11 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.xenondevs.invui.gui.structure.Structure;
 import xyz.xenondevs.invui.inventory.Inventory;
+import xyz.xenondevs.invui.inventory.VirtualInventory;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.stream.Collectors;
+import java.util.function.BiConsumer;
-import java.util.stream.IntStream;
 
 /**
  * An {@link AbstractPagedGui} where every page is its own {@link Inventory}.
@@ -18,7 +18,7 @@ import java.util.stream.IntStream;
  */
 final class PagedInventoriesGuiImpl extends AbstractPagedGui<Inventory> {
     
-    private List<Inventory> inventories;
+    private final @NotNull BiConsumer<@NotNull Integer, @NotNull Integer> resizeHandler = (from, to) -> bake();
     
     /**
      * Creates a new {@link PagedInventoriesGuiImpl}.
@@ -44,29 +44,57 @@ final class PagedInventoriesGuiImpl extends AbstractPagedGui<Inventory> {
         setContent(inventories);
     }
     
+    @SuppressWarnings("DuplicatedCode")
     @Override
-    public int getPageAmount() {
+    public void setContent(@Nullable List<Inventory> content) {
-        return inventories.size();
+        // remove resize handlers from previous inventories
+        if (this.content != null) {
+            for (Inventory inventory : this.content) {
+                if (inventory instanceof VirtualInventory) {
+                    ((VirtualInventory) inventory).removeResizeHandler(resizeHandler);
+                }
+            }
+        }
+        
+        // set content, bake pages, update
+        super.setContent(content);
+        
+        // add resize handlers to new inventories
+        if (this.content != null) {
+            for (Inventory inventory : this.content) {
+                if (inventory instanceof VirtualInventory) {
+                    ((VirtualInventory) inventory).addResizeHandler(resizeHandler);
+                }
+            }
+        }
     }
     
     @Override
-    public void setContent(@Nullable List<@NotNull Inventory> inventories) {
+    public void bake() {
-        this.inventories = inventories == null ? new ArrayList<>() : inventories;
+        int contentSize = getContentListSlots().length;
+        
+        List<List<SlotElement>> pages = new ArrayList<>();
+        List<SlotElement> page = new ArrayList<>(contentSize);
+        
+        for (Inventory inventory : content) {
+            for (int slot = 0; slot < inventory.getSize(); slot++) {
+                page.add(new SlotElement.InventorySlotElement(inventory, slot));
+                
+                if (page.size() >= contentSize) {
+                    pages.add(page);
+                    page = new ArrayList<>(contentSize);
+                }
+            }
+        }
+        
+        if (!page.isEmpty()) {
+            pages.add(page);
+        }
+        
+        this.pages = pages;
         update();
     }
     
-    @Override
-    protected List<SlotElement> getPageElements(int page) {
-        if (inventories.size() <= page) return new ArrayList<>();
-        
-        Inventory inventory = inventories.get(page);
-        int size = inventory.getSize();
-        
-        return IntStream.range(0, size)
-            .mapToObj(i -> new SlotElement.InventorySlotElement(inventory, i))
-            .collect(Collectors.toList());
-    }
-    
     public static final class Builder extends AbstractBuilder<Inventory> {
         
         @Override

invui-core/src/main/java/xyz/xenondevs/invui/gui/PagedItemsGuiImpl.java

@@ -7,8 +7,6 @@ import xyz.xenondevs.invui.item.Item;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.function.BiConsumer;
-import java.util.stream.Collectors;
 
 /**
  * An {@link AbstractPagedGui} that is filled with {@link Item Items}.
@@ -18,9 +16,6 @@ import java.util.stream.Collectors;
  */
 final class PagedItemsGuiImpl extends AbstractPagedGui<Item> {
     
-    private List<Item> items;
-    private List<BiConsumer<Integer, Integer>> pageChangeHandlers;
-    
     /**
      * Creates a new {@link PagedItemsGuiImpl}.
      *
@@ -46,25 +41,27 @@ final class PagedItemsGuiImpl extends AbstractPagedGui<Item> {
     }
     
     @Override
-    public int getPageAmount() {
+    public void bake() {
-        return (int) Math.ceil((double) items.size() / (double) getContentListSlots().length);
+        List<Item> items = content;
-    }
+        int contentSize = getContentListSlots().length;
+        List<List<SlotElement>> pages = new ArrayList<>();
         
-    @Override
+        int pageAmount = items.size() / contentSize;
-    public void setContent(@Nullable List<@NotNull Item> items) {
+        for (int pageIdx = 0; pageIdx < pageAmount; pageIdx++) {
-        this.items = items != null ? items : new ArrayList<>();
+            int from = pageIdx * contentSize;
+            int to = Math.min(from + contentSize, items.size());
+            
+            ArrayList<SlotElement> page = new ArrayList<>(contentSize);
+            for (int i = from; i < to; i++) {
+                page.add(new SlotElement.ItemSlotElement(items.get(i)));
+            }
+            pages.add(page);
+        }
+        
+        this.pages = pages;
         update();
     }
     
-    @Override
-    protected List<SlotElement> getPageElements(int page) {
-        int length = getContentListSlots().length;
-        int from = page * length;
-        int to = Math.min(from + length, items.size());
-        
-        return items.subList(from, to).stream().map(SlotElement.ItemSlotElement::new).collect(Collectors.toList());
-    }
-    
     public static final class Builder extends AbstractBuilder<Item> {
         
         @Override

invui-core/src/main/java/xyz/xenondevs/invui/gui/PagedNestedGuiImpl.java

@@ -6,8 +6,6 @@ import xyz.xenondevs.invui.gui.structure.Structure;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.stream.Collectors;
-import java.util.stream.IntStream;
 
 /**
  * An {@link AbstractPagedGui} where every page is its own {@link Gui}.
@@ -17,8 +15,6 @@ import java.util.stream.IntStream;
  */
 final class PagedNestedGuiImpl extends AbstractPagedGui<Gui> {
     
-    private List<Gui> guis;
-    
     /**
      * Creates a new {@link PagedNestedGuiImpl}.
      *
@@ -44,28 +40,21 @@ final class PagedNestedGuiImpl extends AbstractPagedGui<Gui> {
     }
     
     @Override
-    public int getPageAmount() {
+    public void bake() {
-        return guis.size();
+        List<List<SlotElement>> pages = new ArrayList<>();
-    }
+        for (Gui gui : content) {
+            List<SlotElement> page = new ArrayList<>(gui.getSize());
+            for (int slot = 0; slot < gui.getSize(); slot++) {
+                page.add(new SlotElement.LinkedSlotElement(gui, slot));
+            }
             
-    @Override
+            pages.add(page);
-    public void setContent(@Nullable List<@NotNull Gui> guis) {
+        }
-        this.guis = guis == null ? new ArrayList<>() : guis;
+        
+        this.pages = pages;
         update();
     }
     
-    @Override
-    protected List<SlotElement> getPageElements(int page) {
-        if (guis.size() <= page) return new ArrayList<>();
-        
-        Gui gui = guis.get(page);
-        int size = gui.getSize();
-        
-        return IntStream.range(0, size)
-            .mapToObj(i -> new SlotElement.LinkedSlotElement(gui, i))
-            .collect(Collectors.toList());
-    }
-    
     public static final class Builder extends AbstractBuilder<Gui> {
         
         @Override

invui-core/src/main/java/xyz/xenondevs/invui/gui/ScrollGui.java

@@ -193,6 +193,14 @@ public interface ScrollGui<C> extends Gui {
      */
     void setContent(@Nullable List<@NotNull C> content);
     
+    /**
+     * Bakes the elements of this {@link PagedGui} based on the current content.
+     * <p>
+     * This method does not need to be called when using {@link #setContent(List)},
+     * but is required when the size of the content itself changes.
+     */
+    void bake();
+    
     /**
      * Replaces the currently registered scroll handlers with the specified ones.
      *

invui-core/src/main/java/xyz/xenondevs/invui/gui/ScrollInventoryGuiImpl.java

@@ -4,9 +4,11 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import xyz.xenondevs.invui.gui.structure.Structure;
 import xyz.xenondevs.invui.inventory.Inventory;
+import xyz.xenondevs.invui.inventory.VirtualInventory;
 
 import java.util.ArrayList;
 import java.util.List;
+import java.util.function.BiConsumer;
 
 /**
  * A {@link AbstractScrollGui} that uses {@link Inventory VirtualInventories} as content.
@@ -16,8 +18,7 @@ import java.util.List;
  */
 final class ScrollInventoryGuiImpl extends AbstractScrollGui<Inventory> {
     
-    private List<Inventory> inventories;
+    private final @NotNull BiConsumer<@NotNull Integer, @NotNull Integer> resizeHandler = (from, to) -> bake();
-    private List<SlotElement.InventorySlotElement> elements;
     
     /**
      * Creates a new {@link ScrollInventoryGuiImpl}.
@@ -43,31 +44,42 @@ final class ScrollInventoryGuiImpl extends AbstractScrollGui<Inventory> {
         setContent(inventories);
     }
     
+    @SuppressWarnings("DuplicatedCode")
     @Override
-    public void setContent(@Nullable List<@NotNull Inventory> inventories) {
+    public void setContent(@Nullable List<Inventory> content) {
-        this.inventories = inventories != null ? inventories : new ArrayList<>();
+        // remove resize handlers from previous inventories
-        updateElements();
+        if (this.content != null) {
-        update();
+            for (Inventory inventory : this.content) {
-    }
+                if (inventory instanceof VirtualInventory) {
+                    ((VirtualInventory) inventory).removeResizeHandler(resizeHandler);
+                }
+            }
+        }
         
-    private void updateElements() {
+        // set content, bake pages, update
-        elements = new ArrayList<>();
+        super.setContent(content);
-        for (Inventory inventory : inventories) {
+        
-            for (int i = 0; i < inventory.getSize(); i++) {
+        // add resize handlers to new inventories
-                elements.add(new SlotElement.InventorySlotElement(inventory, i));
+        if (this.content != null) {
+            for (Inventory inventory : this.content) {
+                if (inventory instanceof VirtualInventory) {
+                    ((VirtualInventory) inventory).addResizeHandler(resizeHandler);
+                }
             }
         }
     }
     
     @Override
-    protected List<SlotElement.InventorySlotElement> getElements(int from, int to) {
+    public void bake() {
-        return elements.subList(from, Math.min(elements.size(), to));
+        List<SlotElement> elements = new ArrayList<>();
-    }
+        for (Inventory inventory : content) {
+            for (int i = 0; i < inventory.getSize(); i++) {
+                elements.add(new SlotElement.InventorySlotElement(inventory, i));
+            }
+        }
         
-    @Override
+        this.elements = elements;
-    public int getMaxLine() {
+        update();
-        if (elements == null) return 0;
-        return (int) Math.ceil((double) elements.size() / (double) getLineLength()) - 1;
     }
     
     public static final class Builder extends AbstractBuilder<Inventory> {

invui-core/src/main/java/xyz/xenondevs/invui/gui/ScrollItemsGuiImpl.java

@@ -7,7 +7,6 @@ import xyz.xenondevs.invui.item.Item;
 
 import java.util.ArrayList;
 import java.util.List;
-import java.util.stream.Collectors;
 
 /**
  * A {@link AbstractScrollGui} that uses {@link Item Items} as content.
@@ -17,8 +16,6 @@ import java.util.stream.Collectors;
  */
 final class ScrollItemsGuiImpl extends AbstractScrollGui<Item> {
     
-    private List<Item> items;
-    
     /**
      * Creates a new {@link ScrollItemsGuiImpl}.
      *
@@ -44,23 +41,16 @@ final class ScrollItemsGuiImpl extends AbstractScrollGui<Item> {
     }
     
     @Override
-    public void setContent(@Nullable List<@NotNull Item> items) {
+    public void bake() {
-        this.items = items != null ? items : new ArrayList<>();
+        ArrayList<SlotElement> elements = new ArrayList<>(content.size());
+        for (Item item : content) {
+            elements.add(new SlotElement.ItemSlotElement(item));
+        }
+        
+        this.elements = elements;
         update();
     }
     
-    @Override
-    protected List<SlotElement> getElements(int from, int to) {
-        return items.subList(from, Math.min(items.size(), to)).stream()
-            .map(SlotElement.ItemSlotElement::new)
-            .collect(Collectors.toList());
-    }
-    
-    @Override
-    public int getMaxLine() {
-        return (int) Math.ceil((double) items.size() / (double) getLineLength()) - 1;
-    }
-    
     public static final class Builder extends AbstractBuilder<Item> {
         
         @Override

invui-core/src/main/java/xyz/xenondevs/invui/gui/ScrollNestedGuiImpl.java

@@ -15,9 +15,6 @@ import java.util.List;
  */
 final class ScrollNestedGuiImpl extends AbstractScrollGui<Gui> {
     
-    private List<Gui> guis;
-    private List<SlotElement.LinkedSlotElement> elements;
-    
     /**
      * Creates a new {@link ScrollNestedGuiImpl}.
      *
@@ -43,30 +40,16 @@ final class ScrollNestedGuiImpl extends AbstractScrollGui<Gui> {
     }
     
     @Override
-    public void setContent(@Nullable List<@NotNull Gui> guis) {
+    public void bake() {
-        this.guis = guis != null ? guis : new ArrayList<>();
+        ArrayList<SlotElement> elements = new ArrayList<>();
-        updateElements();
+        for (Gui gui : content) {
-        update();
-    }
-    
-    private void updateElements() {
-        elements = new ArrayList<>();
-        for (Gui gui : guis) {
             for (int i = 0; i < gui.getSize(); i++) {
                 elements.add(new SlotElement.LinkedSlotElement(gui, i));
             }
         }
-    }
         
-    @Override
+        this.elements = elements;
-    protected List<SlotElement.LinkedSlotElement> getElements(int from, int to) {
+        update();
-        return elements.subList(from, Math.min(elements.size(), to));
-    }
-    
-    @Override
-    public int getMaxLine() {
-        if (elements == null) return 0;
-        return (int) Math.ceil((double) elements.size() / (double) getLineLength()) - 1;
     }
     
     public static final class Builder extends AbstractBuilder<Gui> {

invui-core/src/main/java/xyz/xenondevs/invui/inventory/VirtualInventory.java

@@ -8,8 +8,11 @@ import xyz.xenondevs.invui.util.DataUtils;
 import xyz.xenondevs.invui.util.ItemUtils;
 
 import java.io.*;
+import java.util.ArrayList;
 import java.util.Arrays;
+import java.util.List;
 import java.util.UUID;
+import java.util.function.BiConsumer;
 
 /**
  * A serializable {@link Inventory} implementation that is identified by a {@link UUID} and backed by a simple {@link ItemStack} array.
@@ -22,6 +25,7 @@ public class VirtualInventory extends Inventory {
     private int size;
     private @Nullable ItemStack @NotNull [] items;
     private int @NotNull [] maxStackSizes;
+    private @Nullable List<@NotNull BiConsumer<@NotNull Integer, @NotNull Integer>> resizeHandlers;
     
     /**
      * Constructs a new {@link VirtualInventory}
@@ -149,6 +153,7 @@ public class VirtualInventory extends Inventory {
         setGuiPriority(inventory.getGuiPriority());
         setPreUpdateHandler(inventory.getPreUpdateHandler());
         setPostUpdateHandler(inventory.getPostUpdateHandler());
+        setResizeHandlers(inventory.getResizeHandlers());
     }
     
     /**
@@ -236,6 +241,46 @@ public class VirtualInventory extends Inventory {
         }
     }
     
+    /**
+     * Sets the handlers that are called every time this {@link VirtualInventory} is resized.
+     *
+     * @param resizeHandlers The handlers to set.
+     */
+    public void setResizeHandlers(@Nullable List<@NotNull BiConsumer<@NotNull Integer, @NotNull Integer>> resizeHandlers) {
+        this.resizeHandlers = resizeHandlers;
+    }
+    
+    /**
+     * Gets the handlers that are called every time this {@link VirtualInventory} is resized.
+     *
+     * @return The handlers.
+     */
+    public @Nullable List<@NotNull BiConsumer<@NotNull Integer, @NotNull Integer>> getResizeHandlers() {
+        return resizeHandlers;
+    }
+    
+    /**
+     * Adds a handler that is called every time this {@link VirtualInventory} is resized.
+     *
+     * @param resizeHandler The handler to add.
+     */
+    public void addResizeHandler(@NotNull BiConsumer<@NotNull Integer, @NotNull Integer> resizeHandler) {
+        if (resizeHandlers == null)
+            resizeHandlers = new ArrayList<>();
+        
+        resizeHandlers.add(resizeHandler);
+    }
+    
+    /**
+     * Removes a handler that is called every time this {@link VirtualInventory} is resized.
+     *
+     * @param resizeHandler The handler to remove.
+     */
+    public void removeResizeHandler(@NotNull BiConsumer<@NotNull Integer, @NotNull Integer> resizeHandler) {
+        if (resizeHandlers != null)
+            resizeHandlers.remove(resizeHandler);
+    }
+    
     /**
      * Changes the size of the {@link VirtualInventory}.
      * <p>
@@ -259,6 +304,13 @@ public class VirtualInventory extends Inventory {
             int stackSize = previousSize != 0 ? maxStackSizes[previousSize - 1] : 64;
             Arrays.fill(maxStackSizes, previousSize, maxStackSizes.length, stackSize);
         }
+        
+        // call resize handlers if present
+        if (resizeHandlers != null) {
+            for (BiConsumer<Integer, Integer> resizeHandler : resizeHandlers) {
+                resizeHandler.accept(previousSize, size);
+            }
+        }
     }
     
     /**